1. Field
One embodiment of the invention relates to a method and apparatus for manufacturing a magnetic recording medium, and more specifically, a method and apparatus for manufacturing a discrete track recording media.
2. Description of the Related Art
To improve tracks of a hard disk drive (HDD), the problem of interference between adjacent tracks has become obvious. In particular, reduction in write-blur due to a fringe effect of a write head magnetic field is an important technical problem. A discrete track recording media (DTR media) in which recording tracks are physically separated can reduce a side-erase phenomenon at the time of writing, a side-read phenomenon that pieces of information in adjacent tracks are mixed up at the time of reading. Consequently, it is possible to greatly improve a density in the cross-track direction, which can provide a magnetic recording medium onto which high-density recording is possible. However, in a case of a DTR media having patterns of protrusions and recesses on the surface thereof, the problem that it is extremely difficult to write and read by using a low-flying head is brought about. Then, it is necessary to completely flatten the protrusions and recesses by forming a flattening film and etching back the film.
On the other hand, in an HDD, a distance (spacing) between a surface of a recording medium and a read/write head has great effect on a signal-to-noise ratio (SNR). In a state in which a flattening film remains above a ferromagnetic recording layer, spacing is made greater, and an SNR declines (an SNR declines exponentially with spacing). When a flattening film is over-etched, spacing is made favorable, but a magnetic substance is damaged, so that an SNR declines. In a case where an R/W evaluation is performed with a read/write head with a flying height of 12 nm, any readout signal cannot be observed if the flattening film of 10 nm or more remains on a diamond-like carbon (DLC) protective film formed above the ferromagnetic recording layer. Further, when 10 nm or more of the ferromagnetic recording layer (half of the thickness of the ferromagnetic recording layer) is etched by over-etch back, any readout signal cannot be observed. Accordingly, a highly accurate method for detecting an end point of etch-back is necessary to prevent SNR from declining.
However, in a flattening film forming step and an etch-back step for a DTR media under the present status, it is impossible to high-accurately detect an end point of etch-back due to many unstable factors. Specifically, there are problems that a deposition rate of an embedding material by bias sputtering is unstable at the time of forming a flattening film and that an etching rate is unstable because a nonmagnetic material eliminated by etch-back is redeposited in a large quantity to an inner wall of an etching apparatus. Accordingly, in detection of an end point of time-controlled etch-back based on an etching rate, it is impossible to detect an end point of etch-back high-accurately with high-reproducibility.
As a method except for the detection of an end point of time-controlled etch-back based on an etching rate, there is a method in which an end point is detected by carrying out analysis on residual gas in a process chamber in an etch-back step.
In Jpn. Pat. Appln. KOKAI Publication No. 10-209128, there is described a method in which a silicon nitride film is formed as a film to be detected under a spin-on-glass (SOG) film serving as a flattening film in a process of manufacturing a semiconductor apparatus, and an end point of etch-back is determined by monitoring emission of N2 from the film to be detected in the process of etch-back. In Jpn. Pat. Appln. KOKAI Publication No. 6-244150, there is described a method in which a silicon oxide film containing no hydrogen and a silicon oxide film containing hydrogen are laminated in a process of manufacturing a semiconductor apparatus, and an end point of etch-back is detected by monitoring emission of hydrogen atoms in a plasma at the time of etching one of the laminated films by using the plasma.
In this way, in a process of manufacturing a semiconductor, a plasma process in which emission occurs (for example, reactive ion etching (RIE) or the like) can be used, and additionally high sensitivity can be obtained with respect to even a slight change because amplification is possible by using an electron multiplier or the like. However, because ion beam etching without emission is used in a process of manufacturing a DTR media, an end point of etch-back cannot be detected by monitoring emission.
Jpn. Pat. Appln. KOKAI Publication No. 11-265878 describes a method in which, a quadrupole mass spectrometer (Q-Mass) is built into a process chamber, and an end point of etch-back is detected by monitoring a change over time in peaks of the maximum intensity mass number corresponding to a material composition of a flattening film. In Jpn. Pat. Appln. KOKAI Publication No. 11-265878, an end point can be detected with high-sensitivity because a peak intensity of SiBr (mass number 107) to be detected is great.
Because a peak intensity of a material of a flattening film to be used for a DTR media is low, however, sensitivity to detection of an end point greatly declines.